It is hazardous to drive eastbound during sunrise or westbound during sunset. While you need to see the road, you see the sun right under the shade too. The shade may block the sunshine if you raise your head, but it blocks the view of the road too. You usually need sunglasses to reduce the brightness of the sunshine and to minimize the problem. But when you forget to wear your sunglasses, you may actually want to see through the shade or wish that the shade could be semitransparent, and have one particular spot darker where the sun shines brightest. This problem could be solved by inventing a semitransparent, light intensity automatically controlled car shade that allows the driver to see the road during sunrise and sunset.
1. Field of the Invention
This invention relates to the polariscope, the adjustable light transmission device, the sun visor for use in the cockpit of aircraft, and the polarizing window. Particularly, the invention provides a movable, screen darkening spot to block the sun in a curved road and a lighter, semitransparent shade for the driver to see the road.
2. Background Information
In order to provide background information so that the invention may be completely understood and appreciated in the proper context, reference may be made to a number of prior art patents and publications as follows:
In Section 1.6 of the book, `Photoelastic Coating`, by Zandman, Redner, and Dally, published by the Iowa State University Press in 1977, the plane-transmission polariscope is explained. It is the simplest light intensity control system since it consists of only two linear polarizers in parallel and a light source arranged as shown in its FIG. 1.7(a). In the polariscope, the light is first reduced by the first polarizer, and blocked totally by the second polarizer, or analyzer. This is the concept of the light intensity control device, a screen shade or a sun visor.
U.S. Pat. No. 3,521,300, Automatic Electric Self-Synchronizing Polarizing Window, to Weiss in 1970, discloses that a first polarizer is positioned solidly over a window opening of the aircraft cabin, and a second polarizer, or window, is driven to rotate by means of friction rollers at the rim.
U.S. Pat. No. 3,635,543, Variable Light Transmission Device, to Collins in 1972, discloses at least two disks of polarizers that are mounted overlapping in a housing with a rectangular polarizer to provide a variable light transmitting device. In this invention, disks can be rotated but cannot be moved linearly. To cover the whole area of car shade or variation of sunshine direction, it intends to use more than two circular disks. Constantly adjusting and rotating more than two disks on the road independently to control the sunshine may be hard to a driver. Also, this invention will use more than two disks to create overlapping areas. If the road is straight, the device will provide a screen shade after the driver pivots all disks properly.
U.S. Pat. No. 5,115,341, Sun Visor, to Bentley in 1992, discloses that one rectangular polarizer is fixed in the cockpit of an aircraft to reduce the sunlight as a visor, and a movable disk polarizer controls the sun light further. The disk has two opposed snubs as stop. These snubs are used to facilitate the rotation of the disk and the pilot can quickly adjust the visor by turning the disk, using one hand. But if it is pushed and turned by one snub, the disk will rotate and slide simultaneously. You need two hands to turn the disk evenly to prevent sliding and to push the disk evenly for linear motion to avoid rotation. If the sunshine comes in a different direction, the disk must be moved linearly with its polarization axis fixed.
Whatever the precise merits, features and advantages of the above cited references, none of them achieves or fulfills the purposes of the present invention to reduce and control the sunlight intensity at a selected, precise location. Basically, the second disk polarizer should be moved linearly to screen the sunshine directly. But the linear motion should not interfere with the polarization axis of the disk polarizer after the axis is selected independently through rotation.